From top to bottom, a physical layer of a 100G Ethernet includes a PCS (Physical Coding Sublayer, physical coding sublayer), a PMA (Physical Medium Attachment, physical medium attachment) sublayer, and a PMD (Physical Media Dependent, physical media dependent) sublayer. The PCS is located between an RS (Reconciliation Sublayer, reconciliation sublayer) of a MAC (Media Access Control, media access control) layer and the PMA sublayer. An interface between the PCS and an upper-layer RS/MAC sublayer is provided by an XGMII (XG Media Independence Interface, media independent interface, where for the 100G Ethernet, “CGMII” is used to indicate 100G). The PCS is used to map one Ethernet MAC function to a function of an encoding physical layer signal system. Currently, the 100G Ethernet standard 802.3ba stipulates that PCS encoding uses 64B/66B encoding.
64B/66B encoding is used to perform encoding mapping on each character in eight pieces of 8-bit (8-bit) data and one 8-bit control signal that are transmitted through an XGMII, so as to generate a block payload (Block Payload), a sync header (sync header), and a block type field (Block Type Field); and use the three to generate a 66-bit block (Block) in a format and output the block. The block type field (Block Type Field) is used to ensure that a Hamming distance between 64-bit blocks is not less than 4.
FIG. 1 is a codeword conversion format table of 64B/66B encoding provided in the existing 802.3ba standard. Dn indicates an 8-bit data block, Cn indicates a control block (which has 8 bits before encoding and 7 bits after encoding), O0 indicates an Order sequence (order sequence) indication, and Tn indicates a location of packet trailer Terminate of a data packet. It can be seen that a 64-bit all-data block (that is, the 64-bit all-data block does not include a control block and can be represented as data blocks) cannot be compressed; and a 64-bit non-all-data block (that is, the 64-bit non-all-data block includes a control block and can be represented as control blocks) can be compressed into 56 bits, and the remaining 8 bits are used as Block Type Field space to ensure that a Hamming distance between 64-bit blocks, such as control information, for example, Terminate (terminate), Start (start), Order sequence (order sequence), and Control (control), is not less than 4.
As the 400G Ethernet standard is put forward, because technologies such as high-speed interfaces and high-order modulation are used, using an RS-FEC (Reed-Solomon Forward Error Correction, Reed-Solomon Forward Error Correction) scheme with a higher gain becomes a future development trend; however, a 64B/66B encoding method cannot meet a requirement of an RS-FEC algorithm.